Method of making an electrode assembly



Nov. 15, 1938. F. 67 BUDNICK METHOD OF MAKING AN ELECTRODE ASSEMBLY Filed July 15, 1936 Patented Nov. 15, 1938 UNITED STATES PATENT OFFICE METHOD OF MAKING AN ELECTRODE ASSEMBLY Claims.

This invention relates to improvements in luminous electric discharge tubes, generally characterized in the trade as neon tubes and in which rarefied gases, such as neon, argon, helium, krypton, and zenon gases and combinations thereof, are utilized; the invention having for an object to provide a novel and highly advantageous method for producing a glass envelope or container for discharge tube electrodes commonly used in connection with such tubes or lamps.

Heretofore, in the manufacture of electrodes of the above mentioned character, it has been universal manufacturing practice to provide each individual metal electrode with a glass envelope,

then to so arrange the lead-in wires of. the electrode that they extend through and beyond one of the tubes open ends, following which said end is closed or sealed about an intermediate portion of the lead-in wires, hence, locking the electrode in housed relation with respect to its envelope. The remaining end of the envelope is usually left open, with the result that the metal electrode therein is subjected to the well recognized detrimental influences of the atmosphere, bringing about corrosion, rusting and/or oxidation thereof, as well as permitting dust and other foreign matter to be deposited upon the metal electrode surfaces, thus greatly reducing its operating efficiency.

In some types of metal electrodes, 1. e., metal electrodes whose surfaces are chemically coated, it is necessary to close or seal the normally open or inner end of the electrode envelope, whereby to prevent premature deterioration of the chemical coating upon such electrode (compositions of rare alkali earths, etc.) through atmospherical contact or subjection, though in such instances, it is the custom to close said inner end of the electrode envelope without regard for the amount or the character of air trapped therein and in contact with the metal electrode. Whereas such character of closing of the individual metal electrode containing envelope serves, after a fashion, to lessen deterioration of the metal electrode and/or its chemical coating, and to prevent the accumulation of dust and other foreign matter thereupon, the stated expedient does not provide an eiificient packaging of the metal electrode and permits of marked efficiency losses in the coated electrode, primarily, by reason of the air trapped in the closed envelope.

Moreover, where metal electrodes, each provided with individual glass envelopes are utilized. considerable annoyance and difficulty is experienced by a user in properly matching a pair of electrodes to be attached to or installed upon a luminous electric discharge tube whereby to attain most efficient operating results. In explanation of the above statement, it is essential to proper functioning of a luminous electric discharge tube of. the character herein concerned, that the utilized electrodes shall be accurately matched as to size, capacity, and physical properties, whereby to insure a uniform electric force over the entire emission surface of each electrode upon energization thereof from a suitable source of electrical potential. In instances where improper matching of the electrodes occurs, as for example where slightly different sizes or slightly differently treated electrodes are used, improper functioning of the equipped luminous electric discharge tube will result, in that the metal electrodes will be heated to dilferent temperatures, thus causing a relatively unsynchronized bombardment of the same, with a resultant sputtering and the giving off and forming of excessive metal deposits on adjacent portions of the luminous tube, soon rendering the same unfit for usage.

Through the medium of my invention I am enabled to produce a vastly improved envelope for electrical discharge tube electrodes, by means of which accurately factory-paired and physically matched tube electrodes will be housed within a single envelope, in a partial vacuum, whereby said electrodes will be preserved in an absolutely corresponding and perfect condition over an infinite period of non-usage, hence, positively insuring their proper function when attached to or installed upon a luminous electric discharge tube.

An important'object of the invention may be stated to reside in the particular method followed or practiced in the production of my improved metal electrode envelopes, whereby the opposite ends of the envelope will be properly formed or shaped with the placement and sealing of the paired and matched metal electrodes therein.

Other objects of the invention will be in part obvious, and in part pointed out hereinafter.

In order that the invention and its mode of operation may be readily understood by those skilled in the art to which it appertains, I have in the accompanying drawing and the detailed description based thereupon, set out several embodiments of my invention.

In this drawing:

Figure 1 is a, fragmentary elevation of a sealing machine illustrating the various burners, the

rotatable table, and one sealing head upon which an electrode assembly, produced in accordance with the invention is mounted;

Figure 2 is an elevation of one form of my improved electrode assembly;

Figure 3 is a fragmentary elevation of. a slightly modified form of envelope for the assembly wherein its intermediate portion is constricted and,

Figure 4 includes a plurality of fragmentary elevational views, the first of which, reading from left to right, show improper formings and closures of the envelope, and the third of which illustrates a proper formation or closure of electrode tube or envelope.

Having more particular reference to the drawing, in connection with which like characters of reference will designate corresponding parts throughout, it is stated in a prefatory sense, that my improved electrode envelope and the method of producing the same can be successfully effected by the usage of different types of machines now well known in the art. For purposes of illustration, however, I have herein chosen a well known type of sealing machine provided with those devices necessary to proper practicing of the invention. The machine comprehends a rotatable table I supported upon a frame (not shown) on which a plurality of relatively circularly spaced tube sealing heads are supported, though in the drawing I have shown but one of said sealing heads, particularly as they are of complemental construction. Liquid or gaseous fuel burners A, B, C, D, and E are supported from the machine frame in relative spaced relation and in proximity to the table I carrying the sealing heads. In heating glass envelopes or tubes upon the machine, the head 2 is rotated in a direction to progressively bring it into registration with, first, the preheating fiame from the burner A, second, a hotter flame from the burner B, third, between the opposed maximum heating burners C and D where the adjacent portion of the glass envelope or tube is brought, as the result of heat applied thereto, to a plastic or semi-molten form, whereupon it is sealed or closed, and finally, with an annealing flame produced by the burner E. The end sealing or closing operation effected upon the glass envelope or tube while it is in registration with the flames produced by the burners C and D is caused by means of opposed pinching jaws 3 pivotally mounted as at 4 upon the standard 5 of the sealing head 2; said jaws being adapted to be collectively moved into and out of engagement with the plastic or semi-molten end of a glass envelope or tube by means of suitable operating mechanism activatable, at will, by the machine operator.

The sealing head 2 has its standard 5 provided with means for receiving and supporting one end of a vertically disposed glass envelope thereupon, as shown in the Figure 1, and to additionally secure such envelope in its supported engagement upon the sealing head, envelope engaging or gripping fingers 6 of well known con struction are supported from an appropriate portion of the sealing head and engage with an adjacent portion of the envelope.

Positioned in proximity to and above the burner E is a downwardly directed air jet or nozzle 1, the pipe of which is equipped with a hand actuatable valve 8. The air nozzle pipe 9 communicates with a suitable blower intaking air at the temperature of the room or other space in which the sealing machine is mounted. The nozzle 1 is so disposed that air will be discharged or jetted therefrom onto the upper end of the electrode envelope IQ whose lower and remaining end has been sealed between the maximum heating burners C and D and then moved into registration with the annealing flame of the burner E, such air coursing or flowing downwardly over the entire length of the electrode envelope If! for a purpose which will be hereinafter more fully described. In this connection, it is to be understood that the jetting of air at room temperature onto the electrode envelope I is effected simultaneously with its subjection to the annealing flame of the burner E and constitutes a final production stage of the electrode assembly, or as it is above termed, the electrode envelope.

Referring now to the construction of my improved electrode envelope or electrode assembly, and particularly, to the Figure 2 of the accompanying drawing, the device consists of a tubular glass envelope IU of length sufficient to permit of longitudinal arrangement of a pair of perfectly matched metal electrodes H and i2 therein, with a predetermined space between the adjacent or inner ends thereof. Lead-in wires l3 are passed through the opposite or outer ends of the envelope 10 into fixed engagement with adjacent ends of their respective metal electrodes H and I2 and are sealed in the opposite or outer ends of said envelope I0, in the usual manner, as indicated by the numeral l4. Mica discs or similar spacing elements I are preferably engaged with the inner end portions of each of the metal electrodes II and I2 and contact, about their outer peripheries with the adjacent inner peripheral portions of said envelope l0, serving to effectually space the inner end portions of the electrodes ll and'IZ from the envelope Ill.

The electrode envelope l0 may be formed plain or of the same area throughout, as illustrated in the Figure 2. However, if desired, an intermediate portion of said envelope may be constricted, or reduced, as at [6, whereby to provide for convenience in attaching or welding respective electrode assemblies to gaseous discharge tubes of different sizes. The formation, of course, is old in the art to which the invention pertains.

In producing matched or paired electrodes in accordance with my invention, a glass tube, of suitable cross-sectional size and length is utilized. Into one of the open ends of this tube, a metal electrode, such as herein designated by the numerals I I and I 2' is inserted with the lead-in wires extending outwardly of or beyond the receiving end of said tube. The lead-in wires are engaged in the upper end of the standard 5 of the sealing head 2 and the adjacent end of the envelope tube rests thereupon so that the tube is supported in a vertical position and in parallelism to the aforesaid inserted metal electrode. The tube is furthermore firmly secured or supported in its vertical position by engaging the gripping fingers 6 with an intermediate portion thereof, preferably well above its lower and open end. At this time, the table I carrying the sealing head is rotated, bringing said head and the glass tube into registration with the preheating burner A. The preheating flame from the burner A will be directed onto the lower portion of the tube and when the proper preheating of the tube has been effected, the table is further rotated to bring said tube into communication and registration with the.

second stage heating flames produced by the burner B. The tube is then heated to the proper temperature, whereupon the table is again rotated to bring the sealing head and said tube between the maximum heating burners C and D. The flames from these burners will be directed onto the lower portion of the tube from opposite sides and they will heat the lower portion of the tube until it assumes a plastic or semi-molten state. As said lower portion of the tube is heated to a plastic condition, the open end thereof will be constricted or inwardly turned, primarily, because of the pressure of the heating flames applied thereto. At this instant, the sealing or pinching jaws 3 of the sealing head are operated to bring them into collective engagement with the opposite sides of the now plastic lower end of the tube, thus closing or sealing the same, and also, sealing the lead-in wires I3 of the aforesaid metal electrode therein, as hereinbefore indicated by the numeral l4. Immediately with sealing of the lower end of the tube, the table is again rotated to bring said tube into communication with the annealing flame of the burner E, after which, further rotation of the table is effected and the tube, with its lower end sealed, is removed from the standard 5 of the sealing head.

At this time, it will be understood that one end of the tube or electrode envelope is sealed and that its remaining end is open.

A metal electrode is now inserted into the remaining open end of the envelope Ill with its lead-in wires l3 extending beyond such open end, and said envelope is then re-engaged in the upper end of the sealing head or the standard 5; the lead-in wires of the last inserted metal electrode being supportingly engaged in the standard and the remaining and open end of the envelope resting upon an adjacent portion of the upper end of said standard so that it is again supported in a vertical position, with the previously sealed end uppermost. The operation of preheating and then fully heating the remaining open and now lower end of the envelope is now repeated, as is the operation of sealing the heated and plastic tube end. When the remaining lower end of the tube or envelope has been sealed, the table I is rotated to move the sealing head 2 and said envelope from between the maximum heating burners C and D, thus bringing the same into engagement with the annealing flame of the burner E. Concurrently with contact of the annealing flame with the sealed envelope, a jet of air at proper pressure and room temperature, is directed onto the upper portion of such. envelope and is flowed or flooded downwardly over the entire area of the envelope from the downwardly directed nozzle 1. The pressure and the temperature at which this air from the nozzle 7 is discharged onto the envelope is sufficient to maintain the temperature of that air trapped in the envelope H3 against either expansion or contraction until the latter has been annealed and become sufficiently hardened or set to positively prevent its subsequent distortion by either expansion or contraction of the air trapped therewithin, whereupon the envelope is removed to a suitable receiving means.

It is of utmost importance that the air trapped within the envelope 10, following sealing of its opposite ends in the manner above described, shall be positively prevented from either contracting or expanding within said envelope l6 during any time when the ends or end portions of said envelope are in a plastic or semi-plastic state, as by the heating thereof from the flames of the preheating and heating burners A, B, C, and D; also, that the temperattue of the air within said envelope shall be such that it will neither expand nor contract therewithin during the application of the annealing flame from the burner E thereto. Of course, when the glass of the envelope ID, to wit, its opposite end sealed portions have become set 01' hardened, the trapped air will not act upon the envelope to distort any portions of the same and thus render it inefficient or unfit for usage.

In illustration of the foregoing, I invite particular reference to the Figure 4 of the accom panying drawing. In one of the views comprehended by this figure, I have shown a fragment of an electrode enevolpe [8, wherein, following sealing of the second or remaining end thereof, the temperature of the air trapped within the envelope was permitted to increase beyond that of the outside atmosphere, causing expansion of the not yet hardened or set heated lower end of the envelope and permitting of an outward blowing or bulging of said end by reason of the overheated and expanding air, as indicated by the numeral l'l. Thus, a ball or globe-lil e end, or in any event, an excessively bulged end is formed at the sealed and aforesaid second mentioned end of the envelope, weakening the device to such an extent that it will fracture with the application of but slight stress thereto. Therefore, it will be understood that a tube so defective is substan tially unfit for usage.

In another of the views comprehended by the Figure 4, I have shown an electrode envelope and designated it by the reference character iii, the purpose of which is to illustrate another faulty operation or handling of the electrode during sealing of its second or remaining end. In this particular construction, immediately following the sealing of the remaining or second end of the envelope Ill the temperature of the air within said envelope was permitted to drop to too low a degree, and by consequence, to contract. This contraction resulted in an inward drawing of the still unset or unhardened heated remaining end of the envelope Ill and in consequence, said end of the envelope took on a pinched-like or inwardly drawn formation, as indicated by the numeral l8, so that when it harden-ed or set, it remained in this condition. A tube end thus formed is incapable of effectual usage, since it will fracture at the point of inward drawing or pinching of the sealed end thereof with the application of but slight stress thereto.

In view of the foregoing, it will be understood that the maintenance of the temperature of that air trapped within the envelope Ill immediately following its sealing at a point to prevent the eX- pansion or contraction thereof is vital, and this desirable expedient is obtained by accurately controlling or maintaining the temperature of the air discharged from the nozzle? onto the envelope ID at the proper temperature and at the proper pressure. Conversely, if the temperature of the air discharged from the nozzle 1 onto the envelope during its annealing process is too high, the air trapped within said envelope will be excessively heated, particularly through the annealing flame E, and will form the distorted end as indicated by the numeral ll upon the envelope, whereas if the temperature of the air discharged from the nozzle 1 onto the envelope Ill is too low, a pinched-like or inwardly drawn formation, as indicated by the numeral I8 and illustrated in connection with the envelope ID, will be effected, since the air trapped within said envelope w will contract, and in contracting will apply a suction to the unset or unhardened portion of the envelope end, hence drawing it inwardly by reason of the suction thus created.

Moreover, I desire to invite particular attention to the fact that metal electrodes housed within electrode envelopes constructed in accordance with my invention will be preserved against deterioration from atmospherical contact. It is true that whereas a certain amount of air will be trapped within the electrode envelope l0, this air, by reason of its previous heat treatment, will be of a minimum quantity and will be thoroughly dry so that it will have the least possible harmful effect upon the electrodes II and I2, even in those instances where such metal electrodes are otherwise coated or chemically treated. The result of this method of preservation is that no matter when the electrodes are used, their condition will be the same as that in which they initially left the producing factory Also, due to the fact that the metal electrodes H and I2 housed within the electrode envelope ID are absolutely physically matched or paired, it will be understood that a workman, when using the device, will be assured of a pair of electrical- 1y perfect or operative electrodes for connection to a neon or other type of electrical discharge tube.

In using electrodes constructed in accordance with my invention, either the type as shown in the Figure 2 or that illustrated in the Figure 3, the user nicks a medial portion of the envelope 10 with a file, whereupon, by a slight tap, the tube ID will evenly break adjacent the starting file nick, thereby producing a pair of individual electrodes for usage. The thus halved portions of the electrode envelope will constitute individual electrode assemblies adapted to be welded or otherwise appropriately joined and operatively connected to an electrical discharge tube. In this particular connection, it may be noted that to sever or halve an electrode envelope such as illustrated in Figure 3 of the accompanying drawing, the intermediate part of the constricted portion l6 thereof is nicked with a file, saw, or other suitable device and an abnormal stress is then imparted to the so treated constricted intermediate portion, causing it to be cleanly and diametrically fractured.

In order that a correct or proper formation of envelope end may be illustrated for comparison with the improperly formed or sealed ends herein designated by the numerals I1 and I8, respectively, the aforesaid Figure 4 presents a View of a properly formed or sealed envelope end, the envelope being fragmentally shown and designated by the reference character lll It will be observed that the sealed end of this particular envelope is so formed as to provide a gradual or substantially tapered-like reduction of the envelope end, in contradistinction to the abrupt jointure of the malformed ends of the envelopes l and l0 between the same and their respective sealed ends. This gradually tapered or reduced formation of the envelope l0 provides the thus finished tube with the maximum of resistance or strength to withstand the normal rigors of usage.

It will be borne in mind that elsewhere herein I have stated that but a minimum amount of air is trapped within a sealed envelope III; also, that this air, by reason of heat treatment of the envelope during its process of sealing, is dry, and consequently, produces the least possible harmful effects upon electrodes contained within the envelopes. However, if desired, at the time of sealing of the remaining open end of the electrode envelope, that air remaining within or trapped in the upper portion of the envelope may be positively replaced by an inert gas, which gas may be injected into the envelope from its open lower end by appropriate means. The air thus displaced will be replaced by an inert gas which will have absolutely no detrimental or harmful effect upon metal electrodes housed within the envelope, whether they be chemically coated or otherwise treated, or without such character of treatment. To effect this referred to air displacement from an electrode envelope with an inert gas, I provide an upwardly directed discharge nozzle IS in proximity to the burners C and D and so positioned that it will discharge said inert gas upwardly through the remaining open end of the envelope thereinto; the flowing of gas being preferably controlled through a valve 20 and its pressure being quite sufficient to effect the referred to air displacement. When the air has been displaced, the envelope end is sealed, in the manner hereinbefore described.

Manifestly, the construction shown is capable of further modification, and such modification as is within the scope of my claims, I consider within the spirit of my invention.

I claim:

1. The herein described method of producing an electrode assembly which consists of first heating one open end portion of the assembly envelope to a plastic state and pressing it closed over the lead-in wires of an electrode in the envelope, then heating the remaining open end portion of the envelope to a plastic state and pressing the same closed over the lead-in wires of a second electrode in the envelope, then subjecting the closed envelope to an annealing heat and simultaneously controlling the internal temperature of the envelope for preventing the expansion or contraction of air trapped therein while the heated portions of the envelope harden.

2. The herein described method of producing an electrode assembly, which comprises heating the open end portions of the assembly envelope to a plastic state and pressing the same closed over the respective lead-in wires of electrodes within the envelope, then subjecting the closed envelope to an annealing heat and simultaneously controlling the internal temperature of the envelope for preventing the expansion or contraction of air trapped therein until the heated portions thereof harden.

3. The herein described method of producing an electrode assembly which consists of heating the open end portions of the assembly envelope to a plastic state and pressing them closed over the respective lead-in wires of electrodes within the envelope, then subjecting the closed envelope to an annealing heat and simultaneously flowing air at a predetermined temperature entirely over the closed envelope to control the internal temperature of said envelope for preventing the expansion or contraction of air trapped therein until the heated and closed portions have hardened.

4. The herein described method of producing an electrode assembly, which consists of heating the open end portions of the assembly envelope to a plastic state and pressing them closed over the respective lead-in wires of electrodes received in the envelope, then subjecting the closed envelope to an annealing heat and simultaneously controlling the internal temperature of the envelope to prevent expansion or contraction of the air trapped therein during hardening of the closed portion thereof.

5. The herein described method of producing an electrode assembly, which consists of heating the open end portions of an electrode assembly envelope to plastic state and pressing them closed over the respective lead-in wires of the electrode within said envelope, thereupon subjecting the end closed portions of the envelope to an annealing heat, and finally reducing the temperature of air trapped within the envelope to a predetermined degree where the same will neither expand nor contract within such envelope and maintaining such reduction of temperature until the heated and closed ends of the envelope have definitely set.

FRANK O. BUDNICK. 

